To combine two lists to form a third list, use
append(Prefix, Suffix, List).
To analyze a list into its component lists in various ways, use
append/3 with List instantiated to a proper list. The
reference page for append/3 includes examples of its usage,
including backtracking.
To check the length of a list call length(List, Length).
To produce a list of a certain length, use length/2 with
Length instantiated and List partly uninstantiated.
To check if a term is the element of a list, use memberchk(Element, List).
To enumerate the elements of a list via backtracking, use member(Element, List).
To check that a term is NOT the element of a list, use nonmember(Element, List),
which is equivalent to \+member(Element, List).